One of the problems related to the streaming delivery such as moving image delivery is a burst problem. For example, if a large number of packets are delivered in a short period time, a buffer (queue) of relays (including a switch, a router, and a converter) and a transmission destination apparatus overflow. An overflow packet is discarded, and as a result, a reproduced image in the moving image delivery is subject to an image disturbance. This is referred to as the burst problem.
Techniques called traffic shaving and traffic policing to alleviate the burst problem are known. In the traffic shaving technique, a packet to be transmitted is temporarily stored on a buffer, and is then transferred at a constant time interval. In the traffic policing technique, packets are discarded if traffic increases above a constant rate.
An underflow (a scarce state of packets dwelling on the queue) causes a failure in the transmission of the packets at regular intervals. Traffic shaving is implemented to cause a large number of packets to continuously dwell on a queue and to prevent underflow. For this reason, in traffic shaving, the transmission is performed in a state that a delay of time corresponding to a large number of packets dwelling on the queue continuously occurs. If the transmission is interrupted for a certain period of time for any reason in traffic shaving, the number of packets dwelling on the queue is increased even more.
Packet discarding tends to occur in traffic policing. Since a large number of packets are unlikely to be discarded at a time in traffic policing, the possibility of a large image distortion is small. But a small-scale image distortion is still likely to happen because of a small number of discarded packets.
Related arts are described in Japanese Laid-open Patent Publication Nos. 2004-186882 and 2007-13449.